A guide image including a character string or any other similar image is projected in some cases as described, for example, in Japanese Patent Publication No. 2009-118300. In this case, it is assumed that focus adjustment has been carried out and a user can read the character string.
When a projector, a screen, or any other objects is moved after the focus adjustment, however, the focus adjustment is no longer effective and the user may not be able to read the character string. Further, for example, in a projector configured in such away that trapezoidal distortion correction is automatically performed after the projector is moved, the projector projects an image containing a character string that prompts the user to check whether the trapezoidal distortion correction can be performed so that a wrong operation will not trigger any trapezoidal distortion correction. In this case as well, the focus adjustment is not carried out and the user may not be able to read the character string.